Lubricant composition

ABSTRACT

A lubricant composition and a method of lubricating off-road vehicles and/or machinery. The lubricant composition includes (i) a base oil, (ii) at least one ashless component (A) having the structure P(═S)(SR 1 )(OR 2 )(OR 3 ), wherein R 1 , R 2  and R 3  are independently selected form the group consisting of alkyl, aryl, alkylaryl, cycloalkyl, alcohol, carboxylic acid and ester having 1 to 24 carbon atoms; and (iii) at least one component (B) being a metal dialkyl dithio phosphate salt. The total of ashless components (A) provides to the lubricant composition from 0.010 to 0.080 wt. % phosphorus based on the total weight of the lubricant composition and the total of components (B) provides to the lubricant composition from 0.010 to 0.080 wt. % phosphorus based on the total weight of the lubricant composition.

TECHNICAL FIELD

The invention relates to a lubricant composition, in particular alubricant composition used for lubricating a transmission, final driveand wet brake. Furthermore, the invention relates to the use of alubricant composition for off-road applications.

BACKGROUND AND SUMMARY

Modern heavy vehicle machinery, for example earth moving equipment, iscontinually updated to meet increasing consumer demands. Significantimprovements in transmissions and final drives in heavy vehiclemachinery have increased equipment durability and productivity and newand diverse friction materials are continually being developed tofurther enhance performance. Providing the correct lubricants to supportthese new designs plays a significant role in achieving maximum life andperformance for the vehicle.

In the early 1990s, Caterpillar Corporation introduced a new set oftransmission and drive train fluid requirements, designated as“Caterpillar TO-4” specification (version Jun. 23, 2005), for use inCaterpillar's heavy vehicle machinery. Lubricant compositions which meetthe requirements of the “Caterpillar TO-4” specification are consideredto be suitable for off-road applications. All Caterpillar TO-4 lubricantcompositions must comply with a number of fluid properties includingcertain wear, viscometric and friction conditions as set out in theCaterpillar TO-4 specification. Many of the additives used in finaldrive and powershift transmission (FDPT) lubricants are multifunctionaland there is often a conflict generated between properties, such as thescuffing load capacity, copper corrosion performance and bearing pittingperformance. These conflicts inevitably mean that additives must becarefully selected and balanced. Accordingly, it has proven difficultfor additive companies to meet Caterpillar TO-4 requirements, much lessimprove significantly on any of the performance thresholds.

In particular a Caterpillar TO-4 compliant lubricant composition has tofulfill specific requirements as to the dynamic and static frictionproperties of the lubricant composition. Crankcase lubricantcompositions usually do not fulfill the requirements as to the dynamicand static friction properties according to the Caterpillar TO-4specification.

Because crankcase lubricant compositions typically contain frictionmodifiers, e.g. molybdenum containing friction modifiers and organicfriction modifiers like glycerol monooleate, the dynamic and staticfriction properties become too low to qualify as a Caterpillar TO-4compliant lubricant composition.

US 2009/0192063 A1 discloses a lubricating composition comprising an oilof lubricating viscosity formulated with an additive package comprisingat least one overbased metal detergent, at least one neutral metaldetergent and at least one phosphorus-based wear preventative.Furthermore, US 2009/0192063 A1 discloses methods for improvingoxidation performance in a Caterpillar TO-4 fluid for use in heavyvehicle machinery.

The object of the invention is to provide an improved lubricantcomposition, in particular a lubricant composition which meets theCaterpillar TO-4 requirements and has an improved scuffing loadcapacity, copper corrosion performance and bearing pitting performance

The object of invention is solved by a lubricant composition asdisclosed herein. The lubricant composition according to the inventioncomprises a base oil, at least one ashless component (A) having thestructure P(═S)(SR¹)(OR²)(OR³), wherein R¹, R² and R³ are independentlyselected form the group consisting of alkyl, aryl, alkylaryl,cycloalkyl, alcohol, carboxylic acid and ester having 1 to 24 carbonatoms; and at least one component (B) being a metal dialkyl dithiophosphate salt, wherein the total of ashless components (A) provides tothe lubricant composition from 0.010 to 0.080 wt.-% phosphorus based onthe total weight of the lubricant composition and the total ofcomponents (B) provides to the lubricant composition from 0.010 to 0.080wt.-% phosphorus based on the total weight of the lubricant composition.

Surprisingly, the lubricant compositions of the present invention areable to meet the TO-4 specification and have an improved scuffing loadcapacity, copper corrosion performance and/or bearing pittingperformance. In addition, the present invention is able to accomplishthis improvement with a low treat rate additive package which reducesadditive shipping costs, improves plant through-put, and provideseconomic benefits to lubricant blenders in terms of lower net additivetreat costs.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In one embodiment R¹, R² and R³ of the ashless component (A) may beindependently branched or not branched. In another embodiment R¹, R² andR³ may be independently substituted by at least one heteroatom inaddition to carbon and hydrogen, such as chlorine, sulfur, oxygen ornitrogen. In yet another embodiment R¹, R² and R³ independently may have3 to 8 carbon atoms. In still another embodiment R³ may be derived froma reactive olefin and/or is either —CH₂—CHR⁴—C(═O)O—R⁵ orR⁶—OC(═O)CH₂—CH—C(═O)O—R⁷, wherein R⁴ is H or the same as R¹, R² or R³,and R⁵, R⁶ and R⁷ are independently the same as R¹, R² or R³.

The metal of the component (B) may be selected from the group consistingof alkali metals, alkaline earth metals, aluminum, lead, tin,molybdenum, manganese, nickel, copper, titanium, and zinc. In oneembodiment the alkyl groups of the component (B) may contain from 1 to18 carbon atoms. In another embodiment the alkyl groups of the component(B) may be independently selected from ethyl, n-propyl, i-propyl,n-butyl, i-butyl, sec-butyl, amyl, n-hexyl, i-hexyl, n-octyl, decyl,dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl,methylcyclopentyl, propenyl, and butenyl. In yet another embodiment 100mole percent of the alkyl groups of component (B) may be derived fromprimary alcohols. In still another embodiment component (B) comprises atleast one zinc dialkyl dithio phosphate represented by the followingformula:

wherein R₅ and R₆ may be the same or different hydrocarbyl moietiescontaining from 1 to 18 carbon atoms.

The total of ashless components (A) may provide at least 0.015,preferably at least 0.020 wt.-% and/or at most 0.075, preferably at most0.070 wt.-% phosphorus based on the total weight of the lubricantcomposition. In another embodiment the total of ashless components (A)may provide at least 0.025, preferably at least 0.030 wt. % and/or atmost 0.065 to 0.060 wt.-% phosphorus based on the total weight of thelubricant composition. In yet another embodiment the total of ashlesscomponents (A) may provide at least 0.035, preferably at least 0.040 wt.% and/or at most 0.055 to 0.050 wt.-% phosphorus based on the totalweight of the lubricant composition.

The total of components (B) may provide at least 0.015, preferably atleast 0.020 wt.-% and/or at most 0.075, preferably at most 0.070 wt.-%phosphorus based on the total weight of the lubricant composition. Inanother embodiment the total of components (B) may provide at least0.025, preferably at least 0.030 wt. % and/or at most 0.065 to 0.060wt.-% phosphorus based on the total weight of the lubricant composition.In yet another embodiment the total of components (B) may provide atleast 0.035, preferably at least 0.040 wt. % and/or at most 0.055 to0.050 wt.-% phosphorus based on the total weight of the lubricantcomposition.

The total phosphorus content provided by ashless components (A) andcomponents (B) may be from 0.06 to 0.15, preferably 0.07 to 0.14 wt.-%phosphorus based on the total weight of the lubricant composition. Inanother embodiment the total phosphorus content provided by ashlesscomponents (A) and components (B) may be from 0.08 to 0.13, preferably0.09 to 0.12 wt.-% phosphorus based on the total weight of the lubricantcomposition.

The ratio of wt.-% phosphorus based on the total weight of the lubricantcomposition provided by component (A) to wt.-% phosphorus based on thetotal weight of the lubricant composition provided by component (B) maybe from 1:4 to 4:1, preferably from 1:3 to 3:1. In another embodimentthe ratio of wt.-% phosphorus based on the total weight of the lubricantcomposition provided by component (A) to wt.-% phosphorus based on thetotal weight of the lubricant composition provided by component (B) maybe from 1:1.5 to 1.5:1, preferably from 1:1.3 to 1.3:1, more preferablyfrom 1:1.2 to 1.2:1, most preferably 1:1.

The lubricant composition may further comprise at least one component(C) which is a thiadiazole or derivative thereof. In one embodiment thethiadiazole may be 2,5-dimercapto-1,3,4-thiadiazole (DMTD) or aderivative thereof. Derivatives of DMTD may include:2-hydrocarbyldithio-5-mercapto-1,3,4-thiadiazole or2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazole and mixtures thereof;carboxylic esters of DMTD; condensation products of [alpha]-halogenatedaliphatic monocarboxylic acids with DMTD; reaction products ofunsaturated cyclic hydrocarbons and unsaturated ketones with DMTD;reaction products of an aldehyde and a diaryl amine with DMTD; aminesalts of DMTD; dithiocarbamate derivatives of DMTD; reaction products ofan aldehyde, and an alcohol or aromatic hydroxy compound, and DMTD;reaction products of an aldehyde, a mercaptan and DMTD;2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazole; and products fromcombining an oil soluble dispersant with DMTD; and mixtures thereof.

The total of components (C) may provide to the lubricant compositionfrom 0.010 to 0.5 wt.-%, preferably from 0.015 to 0.2 wt.-% sulfur basedon the total weight of the lubricant composition. In another embodimentthe total of components (C) may provide to the lubricant compositionfrom 0.020 to 0.10, preferably from 0.025 to 0.060 wt.-% sulfur based onthe total weight of the lubricant composition.

The base oil used in the lubricant composition may be selected from anyof the base oils in Groups I-V as specified in the American PetroleumInstitute (API) Base Oil Interchangeability Guidelines. Groups I, II,and III are mineral oil process stocks. Group IV base oils contain truesynthetic molecular species, which are produced by polymerization ofolefinically unsaturated hydrocarbons. Many Group V base oils are alsotrue synthetic products and may include diesters, polyol esters,polyalkylene glycols, alkylated aromatics, polyphosphate esters,polyvinyl ethers, and/or polyphenyl ethers, and the like, but may alsobe naturally occurring oils, such as vegetable oils. It should be notedthat although Group III base oils are derived from mineral oil, therigorous processing that these fluids undergo causes their physicalproperties to be very similar to some true synthetics, such as PAOs.Therefore, oils derived from Group III base oils may sometimes bereferred to as synthetic fluids in the industry.

The base oil used in lubricant composition may be a mineral oil, animaloil, vegetable oil, synthetic oil, or mixtures thereof. Suitable oilsmay be derived from hydrocracking, hydrogenation, hydrofinishing,unrefined, refined, and re-refined oils, and mixtures thereof. Unrefinedoils are those derived from a natural, mineral, or synthetic source withor without little further purification treatment. Refined oils aresimilar to unrefined oils except that they have been treated by one ormore purification steps, which may result in the improvement of one ormore properties. Examples of suitable purification techniques aresolvent extraction, secondary distillation, acid or base extraction,filtration, percolation, and the like. Oils refined to the quality of anedible oil may or may not be useful. Edible oils may also be calledwhite oils. In some embodiments, lubricant compositions are free ofedible or white oils. Re-refined oils are also known as reclaimed orreprocessed oils. These oils are obtained in a manner similar to thatused to obtain refined oils using the same or similar processes. Oftenthese oils are additionally processed by techniques directed to removalof spent additives and oil breakdown products.

Mineral oils may include oils obtained by drilling, or from plants andanimals and mixtures thereof. For example such oils may include, but arenot limited to, castor oil, lard oil, olive oil, peanut oil, corn oil,soybean oil, and linseed oil, as well as mineral lubricating oils, suchas liquid petroleum oils and solvent-treated or acid-treated minerallubricating oils of the paraffinic, naphthenic or mixedparaffinic-naphthenic types. Such oils may be partially orfully-hydrogenated, if desired. Oils derived from coal or shale may alsobe useful.

Useful synthetic lubricating oils may include hydrocarbon oils such aspolymerized, oligomerized, or interpolymerized olefins (e.g.,polybutylenes, polypropylenes, propyleneisobutylene copolymers);poly(1-hexenes), poly(1-octenes), trimers or oligomers of 1-decene,e.g., poly(1-decenes), such materials being often referred to asα-olefins, and mixtures thereof; alkyl-benzenes (e.g. dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)-benzenes);polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls);diphenyl alkanes, alkylated diphenyl alkanes, alkylated diphenyl ethersand alkylated diphenyl sulfides and the derivatives, analogs andhomologs thereof or mixtures thereof. Other synthetic lubricating oilsinclude polyol esters, diesters, liquid esters of phosphorus-containingacids (e.g., tricresyl phosphate, trioctyl phosphate, and the diethylester of decane phosphonic acid), or polymeric tetrahydrofurans.Synthetic oils may be produced by Fischer-Tropsch reactions andtypically may be hydroisomerized Fischer-Tropsch hydrocarbons or waxes.In an embodiment, oils may be prepared by a Fischer-Tropschgas-to-liquid synthetic procedure as well as from other gas-to-liquidoils.

The amount of the base oil present may be the balance remaining aftersubtracting from 100 wt. % the sum of the amount of the performanceadditives. For example, the base oil may be present in the lubricantcomposition in an amount greater than 50 wt.-%, greater than 60 wt.-%,greater than 70 wt.-%, greater than 80 wt.-%, greater than 85 wt.-%, orgreater than 90 wt.-%.

The lubricant composition may optionally comprise one or more neutral,low based, or overbased detergents, and mixtures thereof. Suitabledetergent substrates include phenates, sulfur containing phenates,sulfonates, calixarates, salixarates, salicylates, carboxylic acids,carboxylates, phosphorus acids, mono- and/or di-thiophosphoric acids,alkyl phenols, sulfur coupled alkyl phenol compounds and methylenebridged phenols. Suitable detergents and their methods of preparationare described in greater detail in numerous patent publications,including U.S. Pat. No. 7,732,390, and references cited therein.

The detergent substrate may be salted with an alkali or alkaline earthmetal such as, but not limited to, calcium, magnesium, potassium,sodium, lithium, barium, or mixtures thereof. In some embodiments, thedetergent is free of barium. A suitable detergent may include alkali oralkaline earth metal salts of petroleum sulfonic acids and long chainmono- or dialkylarylsulfonic acids with the aryl group being one ofbenzyl, tolyl, and xylyl.

Overbased detergent additives are well known in the art and may bealkali or alkaline earth metal overbased detergent additives. Suchdetergent additives may be prepared by reacting a metal oxide or metalhydroxide with a substrate and carbon dioxide gas. The substrate may bean acid, for example, an acid such as an aliphatic substituted sulfonicacid, an aliphatic substituted carboxylic acid, or an aliphaticsubstituted phenol.

The terminology “overbased” relates to metal salts, such as metal saltsof sulfonates, carboxylates, and phenates, wherein the amount of metalpresent exceeds the stoichiometric amount. Such salts may have aconversion level in excess of 100% (i.e., they may comprise more than100% of the theoretical amount of metal needed to convert the acid toits “normal,” “neutral” salt). The expression “metal ratio,” oftenabbreviated as MR, is used to designate the ratio of total chemicalequivalents of metal in the overbased salt to chemical equivalents ofthe metal in a neutral salt according to known chemical reactivity andstoichiometry. In a normal or neutral salt, the metal ratio is one andin an overbased salt, the MR, is greater than one. Such salts arecommonly referred to as overbased, hyperbased, or superbased salts andmay be salts of organic sulfur acids, carboxylic acids, or phenols.

The overbased detergent may have a metal ratio of from 1.1:1, or from2:1, or from 4:1, or from 5:1, or from 7:1, or from 10:1. The detergentmay be present at 0.001wt.-% to 20 wt.-%, or 0.01 wt.-% to 10 wt.-%, or0.1 wt.-% to 8 wt. %, or 1 wt. % to 4 wt. %, or greater than 4 wt. % to8 wt. % on the total weight of the lubricant composition.

In one embodiment the lubricant composition may comprise at least onemetal sulfonate detergent, preferably a branched metal sulfonatedetergent. One beneficial effect of using such a detergent is to improvedynamic and/or static friction properties as determined by the SEQ 1223friction test according to the CAT TO-4 specification.

The metal sulfonate detergent may be an overbased alkaline earth metalsulfonate detergent. The overbased alkaline earth metal sulfonate may beformed of a sulfonic acid prepared by sulfonating an aromatic compoundalkylated with an alkyl group made by a process comprising oligomerizingan olefin containing from 3 to 10 carbon atoms, wherein said alkyl groupcontains 16 to 40 carbon atoms. The aromatic compound may be alkylatedwith a linear alkyl group, a branched alkyl group or a mixture thereof.In one embodiment the olefin may be selected from the group consistingof propylene and butylene. In another embodiment the olefin may bebutylene and the alkyl group may contain an average of between 16 and 24carbon atoms.

In a preferred embodiment the overbased alkaline earth metal sulfonatedetergent may be an overbased calcium sulfonate detergent. The overbasedcalcium sulfonate detergent may have a Total Base Number (TBN) rangingfrom 200 to 400 mg KOH/g. In one embodiment the overbased calciumsulfonate detergent may provide to the lubricant composition from 0.01to 0.8 wt.-%, preferably from 0.1 to 0.6 wt.-%, more preferably from0.15 to 0.5 wt.-%, most preferably from 0.2 to 0.4 wt.-%, calcium basedon the total weight of the lubricant composition.

The lubricant composition may optionally further comprise one or moredispersants or mixtures thereof. Dispersants are often known asashless-type dispersants because, prior to mixing in a lubricating oilcomposition, they do not contain ash-forming metals and they do notnormally contribute any ash when added to a lubricant. Ashless-typedispersants are characterized by a polar group attached to a relativelyhigh molecular or weight hydrocarbon chain. Typical ashless dispersantsinclude N-substituted long chain alkenyl succinimides. Examples ofN-substituted long chain alkenyl succinimides include polyisobutylenesuccinimide with number average molecular weight of the polyisobutylenesubstituent in a range of 350 to 5000, or 500 to 3000, or 800 to 2200.Succinimide dispersants and their preparation are disclosed, forinstance in U.S. Pat. No. 7,897,696 and U.S. Pat. No. 4,234,435.Succinimide dispersants are typically an imide formed from a polyamine,typically a poly(ethyleneamine).

In some embodiments the lubricant composition preferably comprises atleast one polyisobutylene succinimide dispersant derived frompolyisobutylene with number average molecular weight in the range 350 to5000, or 500 to 3000, or 800 to 2200. The polyisobutylene succinimidemay be used alone or in combination with other dispersants.

In some embodiments, polyisobutylene (PIB), when included, may havegreater than 50 mol %, greater than 60 mol %, greater than 70 mol %,greater than 80 mol %, or greater than 90 mol % content of terminaldouble bonds. Such a PIB is also referred to as highly reactive PIB(“HR-PIB”). HR-PIB having a number average molecular weight ranging from800 to 5000 is suitable for use in embodiments of the presentdisclosure. Conventional non-highly reactive PIB typically has less than50 mol %, less than 40 mol %, less than 30 mol %, less than 20 mol %, orless than 10 mol % content of terminal double bonds.

An HR-PIB having a number average molecular weight ranging from about900 to about 3000 may be suitable. Such an HR-PIB is commerciallyavailable, or can be synthesized by the polymerization of isobutene inthe presence of a non-chlorinated catalyst such as boron trifluoride, asdescribed in U.S. Pat. No. 4,152,499 and U.S. Pat. No. 5,739,355. Whenused in the aforementioned thermal ene reaction, HR-PIB may lead tohigher conversion rates in the reaction, as well as lower amounts ofsediment formation, due to increased reactivity.

In embodiments the lubricant composition comprises at least onedispersant derived from polyisobutylene succinic anhydride. In anembodiment, the dispersant may be derived from a polyalphaolefin (PAO)succinic anhydride. In an embodiment, the dispersant may be derived fromolefin maleic anhydride copolymer. As an example, the dispersant may bedescribed as a poly-PIBSA. In an embodiment, the dispersant may bederived from an anhydride which is grafted to an ethylene-propylenecopolymer.

One class of suitable dispersants may be Mannich bases. Mannich basesare materials that are formed by the condensation of a higher molecularweight, alkyl substituted phenol, a polyalkylene polyamine, and analdehyde such as formaldehyde. Mannich bases are described in moredetail in U.S. Pat. No. 3,634,515. A suitable class of dispersants maybe high molecular weight esters or half ester amides. The dispersantsmay also be post-treated by conventional methods by reaction with any ofa variety of agents. Among these agents are boron, urea, thiourea,dimercaptothiadiazoles, carbon disulfide, aldehydes, ketones, carboxylicacids, hydrocarbon-substituted succinic anhydrides, maleic anhydride,nitriles, epoxides, carbonates, cyclic carbonates, hindered phenolicesters, and phosphorus compounds. U.S. Pat. No. 7,645,726; U.S.7,214,649; and U.S. 8,048,831 describe some suitable post-treatmentmethods and post-treated products.

The dispersant, if present, can be used in an amount sufficient toprovide up to 20 wt. %, based upon the total weight of the lubricantcomposition. The amount of the dispersant that can be used may be from0.001 wt.-% to 5 wt.-%, preferably from 0.01 wt.-% to 2 wt.-%, morepreferably from 0.1 wt.-% to 1 wt.-%, most preferably from 0.15 wt.-% to0.5 wt.-% based on the total weight of the lubricant composition. In anembodiment the lubricant composition utilizes a mixed dispersant system.

The lubricant composition may optionally contain one or more extremepressure agents. Extreme Pressure (EP) agents that are soluble in theoil include sulfur- and chlorosulfur-containing EP agents, chlorinatedhydrocarbon EP agents and phosphorus EP agents. Examples of such EPagents include chlorinated waxes; organic sulfides and polysulfides suchas sulfurized polyisobutylene, sulfurized fatty acids,dibenzyldisulfide, bis(chlorobenzyl) disulfide, dibutyl tetrasulfide,sulfurized methyl ester of oleic acid, sulfurized alkylphenol,sulfurized dipentene, sulfurized terpene, and sulfurized Diels-Alderadducts; phosphosulfurized hydrocarbons such as the reaction product ofphosphorus sulfide with turpentine or methyl oleate; phosphorus esterssuch as the dihydrocarbyl and trihydrocarbyl phosphites, e.g., dibutylphosphite, diheptyl phosphite, dicyclohexyl phosphite, pentylphenylphosphite; dipentylphenyl phosphite, tridecyl phosphite, distearylphosphite and polypropylene substituted phenyl phosphite; metalthiocarbamates such as zinc dioctyldithiocarbamate and bariumheptylphenol diacid; amine salts of alkyl and dialkylphosphoric acids,including, for example, the amine salt of the reaction product of adialkyldithiophosphoric acid with propylene oxide; and mixtures thereof.Preferred EP agents are sulfurized polyisobutylene and sulfurized fattyacids.

The lubricant composition may contain from 0.001 to 2 wt.-%, preferablyfrom 0.01 to 0.3 wt.-%, more preferably from 0.02 to 0.15 wt.-%, mostpreferably from 0.03 to 0.1 wt.-% of one ore more EP agents based on thetotal weight of the lubricant composition.

The lubricant composition may optionally contain one or more rustinhibitors. Suitable rust inhibitors may be a single compound or amixture of compounds having the property of inhibiting corrosion offerrous metal surfaces. Non-limiting examples of rust inhibitors usefulherein include oil-soluble high molecular weight organic acids, such as2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, oleicacid, linoleic acid, linolenic acid, behenic acid, and cerotic acid, aswell as oil-soluble polycarboxylic acids including dimer and trimeracids, such as those produced from tall oil fatty acids, oleic acid, andlinoleic acid. Other suitable rust inhibitors include long-chain alpha,omega-dicarboxylic acids in the molecular weight range of about 600 toabout 3000 and alkenylsuccinic acids in which the alkenyl group containsabout 10 or more carbon atoms such as, tetrapropenylsuccinic acid,tetradecenylsuccinic acid, and hexadecenylsuccinic acid. Another usefultype of acidic rust inhibitors are the half esters of alkenyl succinicacids having about 8 to about 24 carbon atoms in the alkenyl group withalcohols such as the polyglycols. The corresponding half amides of suchalkenyl succinic acids are also useful. A useful rust inhibitor is ahigh molecular weight organic acid. Preferred rust inhibitors includedinonylnaphthalene sulfonate (NASUL ZS, King Industries, Inc.), dimeracid, polyisobutylene anhydride and tetrapropenyl anhydride.

The rust inhibitor can be used in an amount from 0.001 wt.-% to 5 wt.-%,preferably from 0.01 wt.-% to 3 wt.-%, more preferably from 0.1 wt.-% to2 wt.-%, most preferably from 0.2 wt.-% to 0.8 wt.-%, based upon thetotal weight of the lubricant composition.

The lubricant composition may optionally contain one or moreantioxidants. Antioxidant compounds are known and include, for example,phenates, phenate sulfides, sulfurized olefins, phosphosulfurizedterpenes, sulfurized esters, aromatic amines, alkylated diphenylamines(e.g., nonyl diphenylamine, di-nonyl diphenylamine, octyl diphenylamine,di-octyl diphenylamine), phenyl-alpha-naphthylamines, alkylatedphenyl-alpha-naphthylamines, hindered non-aromatic amines, phenols,hindered phenols, oil-soluble molybdenum compounds, macromolecularantioxidants, or mixtures thereof. Antioxidants may be used alone or incombination.

The hindered phenol antioxidant may contain a secondary butyl and/or atertiary butyl group as a sterically hindering group. The phenol groupmay be further substituted with a hydrocarbyl group and/or a bridginggroup linking to a second aromatic group. Examples of suitable hinderedphenol antioxidants include 2,6-di-tert-butylphenol,4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol,4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, or4-dodecyl-2,6-di-tert-butylphenol. In an embodiment the hindered phenolantioxidant may be an ester and may include, e.g., an addition productderived from 2,6-di-tert-butylphenol and an alkyl acrylate, wherein thealkyl group may contain about 1 to about 18, or about 2 to about 12, orabout 2 to about 8, or about 2 to about 6, or about 4 carbon atoms.

Useful antioxidants may include diarylamines and high molecular weightphenols. In an embodiment, the lubricating oil composition may contain amixture of a diarylamine and a high molecular weight phenol, such thateach antioxidant may be present in an amount sufficient to provide up toabout 5%, by weight of the antioxidant, based upon the final weight ofthe lubricating oil composition. In some embodiments, the antioxidantmay be a mixture of about 0.3 to about 1.5% diarylamine and about 0.4 toabout 2.5% high molecular weight phenol, by weight, based upon the finalweight of the lubricating oil composition.

Examples of suitable olefins that may be sulfurized to form a sulfurizedolefin include propylene, butylene, isobutylene, polyisobutylene,pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene,tridecene, tetradecene, pentadecene, hexadecene, heptadecene,octadecene, nonadecene, eicosene or mixtures thereof. In an embodiment,hexadecene, heptadecene, octadecene, nonadecene, eicosene or mixturesthereof and their dimers, trimers and tetramers are especially usefulolefins. Alternatively, the olefin may be a Diels-Alder adduct of adiene such as 1,3-butadiene and an unsaturated ester, such as,butylacrylate.

Another class of sulfurized olefin includes sulfurized fatty acids andtheir esters. The fatty acids are often obtained from vegetable oil oranimal oil and typically contain about 4 to about 22 carbon atoms.Examples of suitable fatty acids and their esters include triglycerides,oleic acid, linoleic acid, palmitoleic acid or mixtures thereof. Often,the fatty acids are obtained from lard oil, tall oil, peanut oil,soybean oil, cottonseed oil, sunflower seed oil or mixtures thereof.Fatty acids and/or ester may be mixed with olefins, such as α-olefins.

The one or more antioxidant(s) may be present in ranges of from 0.001wt.-% to 20 wt.-%, or 0.01 wt.-% to 15 wt.-%, or 0.1 wt.-% to 10 wt.-%,or 1 wt.-% to 5 wt.-% based on the total weight of the lubricantcomposition.

The lubricant composition may optionally contain one or more viscosityindex improvers. Suitable viscosity index improvers may includepolyolefins, olefin copolymers, ethylene/propylene copolymers,polyisobutenes, hydrogenated styrene-isoprene polymers, styrene/maleicester copolymers, hydrogenated styrene/butadiene copolymers,hydrogenated isoprene polymers, alpha-olefin maleic anhydridecopolymers, polymethacrylates, polyacrylates, polyalkyl styrenes,hydrogenated alkenyl aryl conjugated diene copolymers, or mixturesthereof. Viscosity index improvers may include star polymers andsuitable examples are described in US Publication No. 2012/0101017 A1.

The lubricant composition herein also may optionally contain one or moredispersant viscosity index improvers in addition to a viscosity indeximprover or in lieu of a viscosity index improver. Suitable dispersantviscosity index improvers may include functionalized polyolefins, forexample, ethylene-propylene copolymers that have been functionalizedwith the reaction product of an acylating agent (such as maleicanhydride) and an amine; polymethacrylates functionalized with an amine,or esterified maleic anhydride-styrene copolymers reacted with an amine.

The total amount of viscosity index improver and/or dispersant viscosityindex improver may be from 0.001 wt.-% to 25 wt.-%, or 0.01 wt.-% to 20wt.-%, or 0.1 wt.-% to 15 wt.-%, or 0.1 wt.-% to 12 wt.-%, or 0.5 wt.-%to 10 wt.-% based on the total weight of the lubricant composition.

The lubricant composition may optionally contain one ore more pour pointdepressants. Suitable pour point depressants may include esters ofmaleic anhydride-styrene, polymethacrylates, polymethylmethacrylates,polyacrylates or polyacrylamides or mixtures thereof. Pour pointdepressants may be present in amount from 0.001 wt.-% to 1 wt.-%, or0.01 wt.-% to 0.5 wt.-%, or 0.02 wt.-% to 0.04 wt.-% based upon thetotal weight of the lubricant composition.

The lubricant composition may optionally contain one or more anti foamagents. Suitable antifoam agents may include silicon-based compounds,such as siloxanes. Other antifoam agents may include copolymers of ethylacrylate and 2-ethylhexylacrylate and optionally vinyl acetate. Theantifoam agent can be used in an amount of 0.001 wt.-% to 5 wt.-%,preferably 0.005 wt.-% to 3 wt.-%, more preferably 0.1 wt.-% to 2 wt.-%,based upon the total weight of the lubricant composition.

Furthermore, the lubricant composition may comprise one ore more coppercorrosion inhibitors. In one embodiment the copper corrosion inhibitormay be a tolyltriazole. The copper corrosion inhibitor can be used in anamount of 0.001 wt.-% to 5 wt.-%, preferably 0.005 wt.-% to 3 wt.-%,more preferably 0.1 wt.-% to 2 wt.-%, based upon the total weight of thelubricant composition.

In one embodiment the lubricant composition may comprise one or moredemulsifying agents, such as trialkyl phosphates, polyethylene glycols,polyethylene oxides, polypropylene oxides and (ethylene oxide-propyleneoxide) polymers.

A typical lubricant composition according to the invention may comprisethe components according to table 1. In table 1 the ranges provided forcomponent (A) and component (B) refer to wt.-% phosphorus based on thetotal weight of the lubricant composition. The ranges provided forcomponent (C) refer to wt.-% sulfur based on the total weight of thelubricant composition. The ranges provided for the detergent refer towt.-% calcium based on the total weight of the lubricant composition.The ranges provided for the remaining compounds refer to wt.-% of therespective compound based on the total weight of the lubricantcomposition.

TABLE 1 Component General Preferred Component (A) 0.01-0.08 wt.-% P0.02-0.07 wt.-% P  Component (B) 0.01-0.08 wt.-% P 0.02-0.07 wt.-% P Component (C) 0.01-0.50 wt.-% S  0.025 wt-% S Detergent  0.01-0.80 wt.-%Ca    0.33 wt.-% Ca Dispersant  0.01-2 wt.-%  0.2 wt.-% EP agent     0-2wt.-%  0-0.1 wt.-% Rust inhibitor 0.001-2 wt.-%  0.5 wt.-% Coppercorrosion 0.001-2 wt.-% 0.006 wt.-% inhibitor Antifoam agent 0.001-2wt.-% 0.005 wt.-% Base oil Balance Balance

In one embodiment the lubricant composition may be a Caterpillar TO-4compliant lubricant composition. Accordingly, the lubricant compositionmay be suitable for off-road applications. In particular the lubricantcomposition may be free of molybdenum containing friction modifiersand/or free of glycerol monooleate. Therefore, the dynamic and staticfriction properties as determined by the SEQ 1223 friction testaccording to the CAT TO-4 specification may be further improved.

EXAMPLES

The inventors have prepared a series of working examples E1 to E5 andcomparative examples C1 to C8 as listed in table 2 below. All workingand all comparative examples are lubricant compositions comprising thecomponents according to table 1. The only parameters that were variedare the amounts of ashless component (A) and component (B). The amountsof the remaining components were kept constant for all working and allcomparative examples.

The following tests were conducted to evaluate the working and thecomparative examples:

FZG Scuffing Test

The FZG scuffing test method is used to evaluate the scuffing loadcapacity of lubricant compositions. The test method is ASTM D5182 of2008 which is a standard method used to evaluate the scuffing loadcapacity of fluids. The test method evaluates gear tooth face scuffingresistance of fluids using “A” profile gears. The rig is operated at1450 rpm through up to 12 progressive load stages at 15 minuteintervals. Standard tests are run at a fluid temperature of 90° C. Thetest procedure commences with a comparatively small pre-load of themeshed gears and after a 15 minute test duration the gear teeth areinspected for scuffing. If the gear teeth are determined to have apre-assigned amount of scuffing the test is considered a fail at thatload stage and the test is terminated at that point. If the gear teethdo not have a pre-assigned amount of scuffing an additional load isadded to the meshed gear teeth and the test run for a further 15minutes. This mode of operation is continued until either the gear teethare determined to have failed at a particular load stage or load stage12 is reached without failure. There are no load stages above load stage12, therefore if a fluid is deemed to have acceptable performance afterload stage 12 the test is terminated. In addition to a visual evaluationof gear tooth condition, gear weight loss is measured.

In order for a fluid to meet the requirements of Caterpillar TO-4 theperformance in the ASTM D5182 of 2008 FZG scuffing test must meet theminimum required performance standards as follows:

TABLE 2 SAE viscosity grade Minimum passing load stages 10W 8 30W 8 40W10 50W 10

Copper Corrosion Test

The working and comparative examples were subjected to a modifiedversion of the ASTM D130 of 2012 procedure in which copper strips areimmersed in the lubricant oil for a set duration and given temperature.At test completion, the copper strips are evaluated on the basis ofappearance and weight loss, and the oil is evaluated for levels ofcopper. Higher levels of weight loss and/or copper in oil indicate thecorrosiveness of the lubricant oil to copper. In the working andcomparative examples, the temperature was held at 150° C. for 186 hours.

In table 3 the test results show whether gear distress was identified byeither “pass” or “fail” test results. Thus, “fail” indicates thatsignificant copper strip weight loss was observed at the end of test(>50 mg weight loss. “EOT mg loss” refers to the amount of copperremoved from the copper strip during the test. It is evidence of thecorrosivity of the lubricant composition to copper.

ZF Bearing Pitting Test (Entwicklung eines Lagerpittingtests fuerKNKW-Getriebeoele), NO.: 0000 702 232.

This version replaced 0000 702 232C, 09-10-10 and includes new testbearings with a new cage, having 15 rollers (instead of the previous 17)and a reduction of axial force from 70 kN to 68 kN. Lubricantcompositions that passed both the copper corrosion test and the FZGscuffing test were subjected to an ZF bearing pitting test. As ZFbearing pitting test a modified ZF bearing pitting test (ZFLagerpittingtest) No. 0000 702 232 of 2011-03-21 was conducted. The testconsists of FE-8 cylinder roller thrust bearings operated at a fluidtemperature of 100° C. The bearings are rotated at 300 rpm untilsufficient wear occurs to cause excessive vibration, at which time thetest is stopped. The “hours to failure” indicate the running time untilexcessive vibration. A duration in excess of 100 hours indicates apassing lubricant composition, while those below indicate a failinglubricant composition.

TABLE 3 FZG FZG Copper load load bearing Ashless corrosion stage bearingCopper stage pitting Total P Comp. (B) Comp. (A) in (EOT (LS pittingcorrosion (LS 12 (>100 (wt.-%) (wt.-% P) (wt.-% P) mg loss) pass)(hours) (<50 ppm) pass) hours) E1 0.130 0.065 0.065 26 12 306 Pass PassPass E2 0.100 0.050 0.050 27 12 141 Pass Pass Pass E3 0.076 0.055 0.0218 12 134 Pass Pass Pass E4 0.086 0.022 0.064 1 12 750 Pass Pass Pass E50.070 0.035 0.035 4 12 267 Pass Pass Pass C1 0.132 0.132 0 60 — — Fail —— C2 0.101 0.101 0 −3 12  55 Pass Pass Fail C3 0.070 0.070 0 3 12  89Pass Pass Fail C4 0.117 0.088 0.029 62 — — Fail — — C5 0.115 0.029 0.086121 — — Fail — — C6 0.130 0 0.130 135 — — Fail — — C7 0.100 0 0.100 75 —— Fail — — C8 0.070 0 0.070 264 — — Fail — —

Table 3 shows that working examples E1 to E5 passed the copper corrosiontest, the ZF bearing pitting test and the FZG load stage test. Allworking examples E1 to E5 comprise ashless component (A) as well ascomponent (B), wherein component (A) provides to the lubricantcomposition from 0.010 to 0.080 wt.-% phosphorus based on the totalweight of the lubricant composition and component (B) provides to thelubricant composition from 0.010 to 0.080 wt.-% phosphorus based on thetotal weight of the lubricant composition.

Comparative examples C1 to C3 which do not contain ashless component (A)failed either the copper corrosion test or the ZF bearing pitting testin spite of comprising a wide range of component (B). Comparativeexamples C4 and C5 comprising both, ashless component (A) and component(B), failed the copper corrosion test. In comparative example C4component (B) provides more than 0.08 wt.-% phosphorus based on thetotal weight of the lubricant composition. In comparative example C5ashless component (A) provides more than 0.08 wt.-% phosphorus based onthe total weight of the lubricant composition. Comparative examples C6and C8 which do not contain component (B) failed the copper corrosiontest in spite comprising a wide range of ashless component (A).

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” include plural referents unlessexpressly and unequivocally limited to one referent. Thus, for example,reference to “an antioxidant” includes two or more differentantioxidants. As used herein, the term “include” and its grammaticalvariants are intended to be non-limiting, such that recitation of itemsin a list is not to the exclusion of other like items that can besubstituted or added to the listed items

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that can vary depending upon thedesired properties sought to be obtained by the present disclosure. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

While particular embodiments have been described, alternatives,modifications, variations, improvements, and substantial equivalentsthat are or can be presently unforeseen can arise to applicants orothers skilled in the art. Accordingly, the appended claims as filed andas they can be amended are intended to embrace all such alternatives,modifications variations, improvements, and substantial equivalents.

1. A lubricant composition comprising: (i) a base oil, (ii) at least oneashless component (A) having the structure P(═S)(SR¹)(OR²)(OR³), whereinR¹ is —CH₂—CHR⁴—C(═O)O—R⁵ or —R⁶—OC(═O)CH₂—CH—C(═O)O—R⁷, wherein R² andR³ are independently selected from a hydrocarbyl group having 2 to 8carbon atoms and R⁴ is H or the same as R² or R³ and R⁵, R⁶ and R⁷ areindependently the same as R² or R³; (iii) at least one component (B)being a metal dialkyl dithio phosphate salt, wherein the component (B)comprises at least one zinc dialkyl dithio phosphate represented by thefollowing formula:

wherein R⁸ and R⁹ may be the same or different alkyl groups containingfrom 1 to 18 carbon atom, wherein the total of ashless components (A)provides to the lubricant composition from 0.035 to 0.065 wt.-%phosphorus based on the total weight of the lubricant composition andthe total of components (B) provides to the lubricant composition from0.035 to 0.065 wt.-% phosphorus based on the total weight of thelubricant composition. 2-5. (canceled)
 6. The lubricant compositionaccording to claim 1, wherein the alkyl groups of the component (B) areindependently selected from ethyl, n-propyl, i-propyl, n-butyl, i-butyl,sec-butyl, amyl, n-hexyl, i-hexyl, n-octyl, decyl, dodecyl, octadecyl,2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl,propenyl, and butenyl.
 7. The lubricant composition according to claim1, wherein 100 mole percent of the alkyl groups of the at least onecomponent (B) are derived from primary alcohols. 8-10. (canceled) 11.The lubricant composition according claim 1, wherein the totalphosphorus content provided by ashless components (A) and components (B)is from 0.07 to 0.13 wt.-% phosphorus based on the total weight of thelubricant composition.
 12. The lubricant composition according to claim1, wherein the ratio of wt.-% phosphorus based on the total weight ofthe lubricant composition provided by component (A) to wt.-% phosphorusbased on the total weight of the lubricant composition provided bycomponent (B) is from 1:4 to 4:1. 13-14. (canceled)
 15. The lubricantcomposition according to claim 1, wherein the lubricant compositionfurther comprises at least one overbased alkaline earth metal sulfonatedetergent.
 16. The lubricant composition according to claim 15, whereinthe overbased alkaline earth metal sulfonate is formed of a sulfonicacid prepared by sulfonating an aromatic compound alkylated with analkyl group made by a process comprising oligomerizing an olefincontaining from 3 to 10 carbon atoms, wherein said alkyl group contains16 to 40 carbon atoms.
 17. The lubricant composition according to claim16, wherein said olefin is selected from the group consisting ofpropylene and butylene.
 18. The lubricant composition according to claim17, wherein said olefin is butylene and said alkyl group contains anaverage of between 16 and 24 carbon atoms.
 19. The lubricant compositionaccording to claim 15, wherein said overbased alkaline earth metalsulfonate detergent is an overbased calcium sulfonate detergent.
 20. Thelubricant composition according to claim 19, wherein said overbasedcalcium sulfonate detergent has a Total Base Number (TBN) ranging from200 to 400 mg KOH/g.
 21. A method of lubricating off-road vehiclesand/or machinery comprising providing to the off-road vehicle and/ormachinery, a lubricating oil composition comprising: (i) a base oil,(ii) at least one ashless component (A) having the structureP(═S)(SR¹)(OR²)(OR³), wherein R¹ is —CH₂—CHR⁴—C(═O)O—R⁵ or—R⁶—OC(═O)CH₂—CH—C(═O)O—R⁷, wherein R² and R³ are independently selectedfrom a hydrocarbyl group having 2 to 8 carbon atoms and R⁴ is H or thesame as R² or R³ and R⁵, R⁶ and R⁷ are independently the same as R² orR³; and (iii) at least one component (B) being a zinc dialkyl dithiophosphate salt, wherein the total of ashless components (A) provides tothe lubricant composition from 0.035 to 0.065 wt.-% phosphorus based onthe total weight of the lubricant composition and the total ofcomponents (B) provides to the lubricant composition from 0.035 to 0.065wt.-% phosphorus based on the total weight of the lubricant composition;and operating the off-road vehicle and/or machinery.
 22. The lubricantcomposition according to claim 1, wherein R¹ is —CH₂—CHR⁴—C(═O)O—R⁵, R²is an alkyl group having 3 carbon atoms R³ and R⁵ are independently analkyl group having from 2 to 8 carbon atoms, and R⁴ is H.
 23. Thelubricant composition according to claim 1, further comprising at leastone component (C) comprising a thiadiazole or derivative thereof. 24.The lubricant composition according to claim 23, wherein component (C)is selected from the group consisting of2-hydrocarbyldithio-5-mercapto-1,3,4-thiadiazole or2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazole.
 25. The lubricantcomposition according to claim 24, wherein component (C) is present inan amount sufficient to provide to the lubricant composition from 0.010to 0.5 wt.-% sulfur based on a total weight of the lubricantcomposition.